1976 182P fuel venting issue

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Georgeyk17

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Georgeyk17
Hello all you genius pilots and A&P's. So here's the issue. Our plane just had it's annual in Jan and is running beautifully. Only issue is after a 1 to 2 hour flight while refueling the right side takes only 6 gallons and left side takes 14 gallons of fuel. Looked up a couple of articles and made a slight vent adjustments and got it down to about 8G on the Right and 12G on the Left. Made another adjustment this weekend and it went to 4G on the Left and 12G on the Right (changed this time). So we did another slight adjustment yesterday and it went to 6.5G on the Left and 0G on the right (another complete change of sides).
So we are boggled. Has anyone ever come across this or know what might be going on. We're a little concerned for any long distance travel as the weather is starting to get nice and what to nip this in the but. Thanks in advance.
By the way, this has been an issue prior to the annual for about 6 months now.

GK
 
I fly a182P as well and I'm sure there are all sorts of technical tweaks that can be made and goodness knows the venting system was improved in later models. I've never had a vent blockage but on long flights, I have had an uneven burn.

I actually just switch tanks and run on the right to burn it down if I have to. Installing new digital fuel senders really made it much more comfortable to do this. Unlike the old float senders, I have verified these to a narrow tolerance. One of the best improvements I made.
 
Leaking fuel caps let the low pressure atop the wing to suck on the fuel in the tank, reducing its ability to flow down to the system. The vent crossover tube across the top front of the cabin ceiling is full of fuel when the tanks are full, and it hampers pressure equalization between the tanks. Just removing and resinstalling the caps can change the quality of the seal and affect the venting. And a badly leaking cap can suck all the fuel out and collapse the bladder, holding the fuel gauge ender float up and making the gauge read full. Nasty stuff.

Do you have the flush caps or the retrofitted raised caps? The raised caps have gaskets that get old and crack, and their little silicone rubber check valve ages and collapses and leaks. the flush caps have an AD against them to force inspections annually: https://rgl.faa.gov/Regulatory_and_...7CA32CBFD7107A87862569B9004D1566?OpenDocument

There is an O-ring around the cap that seals against the filler neck, and another inside the cap around the locking shaft. Both get old and crack, and I have found them like that even though the AD mandates that they seal. O-rings aren't expensive. No excuse not to replace them regularly.

Or the flush caps have been modified IAW AD 79-10-14R1 and the vents are leaking.
 
Couple of thoughts to consider...

Check fuel caps. Aircraft Spruce sells the rubber gasket and plastic slip ring. You need both if you have a fuel cap sealing problem. They are inexpensive and good preventive maintenance.

Slightly uncoordinated flight is also a commonly a root cause for unequal fuel balance right/left tank. When the plane is parked for a while post flight, if the fuel roughly re-balances then likely uncoordinated flight is the cause.
 
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The Cessna Pilots Association argument is compelling and they tell you how to fix it. While the cap gaskets should be checked for other reasons (water infiltration) they won't likely be the cause of this problem. While it is easy to blame the pilot for uncontrolled flying, I have no idea why this would cause a problem (at least not at the tank levels we're talking about). Most planes aren't rigged so badly that they don't fly pretty near perfectly coordinated in cruise when all this is happening, anyway.
 
flyingron said:
The Cessna Pilots Association argument is compelling and they tell you how to fix it. While the cap gaskets should be checked for other reasons (water infiltration) they won't likely be the cause of this problem. While it is easy to blame the pilot for uncontrolled flying, I have no idea why this would cause a problem (at least not at the tank levels we're talking about). Most planes aren't rigged so badly that they don't fly pretty near perfectly coordinated in cruise when all this is happening, anyway.
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Flying a Cessna 100 series aircraft slightly uncoordinated for whatever reason will cause fuel transfer from one side to the other through the cross-tank breather tube. Uncoordinated flight could be caused by rigging, slight unintentional slipping, or Turn Coordinator ball out of level (pilot thinking they are coordinated, and not).

It's doesn't take much to shift from one tank to the other.
 
Same issue with my 1976 182P.

After a lot of research on the matter, I just fly switching to the right tank in cruise for some time.

It may act differently full vs partial.

As long as you get it to perform consistently and predictably, you should be fine. Adjust your vent and leave it alone.
 
NordicDave said:
Flying a Cessna 100 series aircraft slightly uncoordinated for whatever reason will cause fuel transfer from one side to the other through the cross-tank breather tube. Uncoordinated flight could be caused by rigging, slight unintentional slipping, or Turn Coordinator ball out of level (pilot thinking they are coordinated, and not).

It's doesn't take much to shift from one tank to the other.
Click to expand...

It will flow through that line whether you are slipping or not. All that is required is the tank level be above the level of the line. Just the difference in tank pressures will do it (read the CPA article).
 
NordicDave said:
Flying a Cessna 100 series aircraft slightly uncoordinated for whatever reason will cause fuel transfer from one side to the other through the cross-tank breather tube. Uncoordinated flight could be caused by rigging, slight unintentional slipping, or Turn Coordinator ball out of level (pilot thinking they are coordinated, and not).

It's doesn't take much to shift from one tank to the other.
Click to expand...

It will also flow through the fuel system via the selector valve when it's on Both. Fuel from the high side runs down, through the valve, and up the other side. Cessna 150s don't have a selector, just a shutoff valve downstream of the tee where the fuel lines join, and they'll do that even with the fuel shut off. Parking on a sloping surface with one wing higher is enough to get it going.
 
flyingron said:
It will flow through that line whether you are slipping or not. All that is required is the tank level be above the level of the line. Just the difference in tank pressures will do it (read the CPA article).
Click to expand...

Agree. It's most common cause for an inflight fuel imbalance for Cessna 182 is slightly uncoordinated flight.

Dan Thomas said:
It will also flow through the fuel system via the selector valve when it's on Both. Fuel from the high side runs down, through the valve, and up the other side. Cessna 150s don't have a selector, just a shutoff valve downstream of the tee where the fuel lines join, and they'll do that even with the fuel shut off. Parking on a sloping surface with one wing higher is enough to get it going.
Click to expand...

Yes, good additional points.
 
Agree. It's most common cause for an inflight fuel imbalance for Cessna 182 is slightly uncoordinated flight.
Click to expand...
I don't know how you can say "Agree" and then come to the opposite conclusion.
 
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